The annual tradition of NORAD tracking Santa's movements has officially begun. For most of the year NORAD is tasked with defending airspace around the US and Canada from missiles and incursions by foreign air forces, but each December it also pours a huge amount of resources into entertaining children around the world by tracking Santa Claus as he delivers presents.

The unusual tradition dates back to 1955, when a Sears department store offered children the chance to talk directly to Santa in an advert. It said: “Hey, Kiddies! Call me direct and be sure and dial the correct number.”

Unfortunately, they hadn't demonstrated the same attention to detail that they were demanding of children and had accidentally printed the phone number for the Continental Air Defense Command (CONAD) instead of their own office. Instead of getting through to an actor, ready with a gruff laugh and some scripted patter, they ended up on the line to a military base. Once he realised what had happened, Colonel Harry Shoup - who came to be known as the “Santa Colonel” - quickly told his staff to answer the calls with an update on Santa's current position.

NORAD replaced CONAD a few years later, but the tradition remained and continues to this day.